Despite the success of antiretroviral therapy (ART), effective treatment outcomes among people with HIV-1 occur in only 1/3rd of the total HIV-1-population who receives treatment. In addition to reduced adherence to ART treatment, consumption of substance of abuse including tobacco smoking, which is highly prevalent in people with HIV-1, is one of the major factors for ineffective treatment outcomes. Smoking is known to exacerbate HIV- 1 pathogenesis in monocytes and macrophages, which serve as sanctuary sites for HIV-1 and infiltrate the brain, spreading the virus to perivascular macrophages and microglia and causing development of neuroAIDS. It is difficult to eliminate the virus in macrophages by ART. In addition, smoking accelerates HIV-1 replication, in part via increased oxidative stress. Our objective is to determine the role of monocytic and plasma exosomal CYP enzymes in enhancing smoking-mediated HIV-1 replication in smokers. We will accomplish our objective by testing the hypotheses that: 1) monocytic CYP enzymes mediate enhanced HIV-1 replication in smokers by contributing to increased oxidative stress and decreased ART efficacy and 2) circulating plasma exosomal CYP enzymes, secreted from liver and lung cells, are induced in smokers and delivered to macrophages contributing to enhanced HIV-1 replication. The rationale for the hypothesis is based on literature reports that smoking exacerbates HIV-1 replication in macrophages. Our own studies suggest that CYP enzymes are induced by tobacco smoking in monocytes and perhaps in plasma exosomes, and play a critical role in oxidative stress and ART metabolism in macrophages. We plan to test the hypotheses by determining the: Aim 1: Contribution of monocytic CYP enzymes in tobacco-enhanced HIV-1 replication in macrophages; Aim 2: Ex vivo validation of the role of CYP enzymes in smoking-enhanced HIV-1 replication; Aim 3: Contribution of plasma exosomal CYP enzymes to HIV-1 replication in macrophages. Upon completion of this project, we expect to determine the mechanistic contributions and gain a new understanding of a novel role of monocytic and plasma exosomal CYP enzymes in smoking-mediated HIV-1 pathogenesis. Thus, the project would impact the treatment of HIV-1 who smoke by providing a new target for novel therapeutic interventions, and potential application of exosomes as therapeutic carriers in effectively treating these patients.